When a visit to an old friend at a rehabilitation center for troubled youth turns violent, Miss Marple must untangle a web of deception hidden behind a staged shooting. Miss Marple arrives at Stonygates, a Victorian mansion serving as a reformatory, only to witness a youth fire a revolver at the administrator, Lewis Serrocold. While the administrator survives, a guest is found murdered in a separate wing of the house, prompting Miss Marple to investigate the true motives behind the visitor's arrival. The narrative unfolds through a third-person perspective, focusing on the keen observation and deductive reasoning of the elderly protagonist as she navigates the complex social dynamics of the mansion's inhabitants.

This novel is widely regarded as a quintessential example of Agatha Christie's ability to manipulate reader perception through misdirection and theatrical staging. The work is frequently cited for its clever use of the 'mirror' metaphor, which serves as a central theme for the deceptive nature of the crime. Readers often note that the setting of a rehabilitation center provides a unique backdrop that allows for a diverse cast of suspicious characters. The narrative structure demonstrates the author's mastery of the traditional whodunit format, ensuring that the final reveal remains both logical and surprising to the audience.